This invention relates generally to circulator devices and more particularly to an improved stripline circulator.
Those skilled in the art will appreciate that circulators are used extensively in radio communication equipment. One well known use of a circulator is to combine a transmitter and receiver to a single antenna. Another use for circulators is to isolate reflected power from a transmitter radio frequency power amplifier. Typically, high power radio frequency amplifiers must operate at a high level of electrical efficiency and be free from parasitic oscillation. In order to achieve these requirements under all load conditions, it is desirable to place a circulator at the output of the power amplifier. In a configuration such as this the forward power will pass through the circulator to the antenna, and reflected power, due to any impedance mismatch, will be terminated into a load.
Prior circulators were typically constructed from discrete mechanical parts. The circulator was assembled by stacking and aligning the ground plane, ferrite substrates and a resonator. Adhesives were commonly applied during the assembly process to maintain proper alignment of the individual parts. Due to the various mechanical and assembly tolerances, prior circulator assembly techniques could not produce a consistent circulator structure, which lead to inconsistent circulator performance. Further, the use of adhesives generally resulted in a circulator with poor temperature performance.
Accordingly, a need exists to find a simple inexpensive circulator that is easy to manufacture and avoids the temperature and tolerance buildup problems of the prior art.